Corrosion-inhibiting compositions



CORROSION-INHIBITING COD [POSITIONS Troy L. Cantrell, Drexel Hill, and Earl E. Fisher, Glenolden, Pa., assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application June 4, 1954, Serial No. 434,642

Claims. (Cl. 25232.5)

This invention relates to corrosion-inhibiting compositions useful in protecting metal surfaces, and more particularly to compositions that are adapted to counteract and/or displace organic or inorganic corrosion-inducing contaminants that have become deposited upon said metal surfaces.

In the manufacture, handling and/ or assembly of various metal articles, it frequently occurs that the surfaces of such articles become contaminated with corrosion-inducing residues, including those resulting from perspiration, fingerprints, pickling solutions, quenching fluids, etc. The problem of protecting metal surfaces against the harmful action of such contaminants is difiicult because of the complexity of these contaminants, which may be either organic or inorganic materials having widely different reactivities, solubility characteristics, and the like;

We have found that the protection of metal surfaces which have been exposed to the actionof corrosion-inducing contaminants is facilitated by treatment thereof with our corrosion-inhibiting composition which comprises a mineral hydrocarbon oil base having incorporated therein from about 5 to about 15 per cent by weight of water, from about 0.25 to about 2.5 per cent by weight of an alkanol amine selected from the group consistingof primary, secondary'and tertiary amines whose alkanol substituents contain from 2 to 3 carbon atoms, from' about 0.1 to about 1.0 per cent by weight of a salt of primary, aliphatic amine containing from 8 to 18 carbon atoms and a dialkyl ester of orthophosphoric acid whose alkyl sub stituents contain from 3 to 10 carbon atoms, from about 1 to about '10 per cent by weight of an alkali metal salt of an oil-soluble sulfonic acid, from about 0.75 to about 7.5 per cent by weight of a fatty acid containing from 12 to 24 carbon atoms, the fatty.acid:alkanol amine mol ratio being in excess of 1:1, from about 5 to about 15 per cent by weight of a coupling agent selected from the group consisting of Z-butoxyethanol and mixtures thereof with butanol, the 2-butoxyethanol being present in the mixture in amounts of from about 1 to about 15 per cent by weight.

In preparing the foregoing composition the components may be admixed in any order Blending of the components is preferably carried out at room temperature, but elevated temperatures below the boiling point of the lowest boiling component may be used, if desired. Blending of the components may be facilitated at all suitnitecl States atent O about'87;9 per cent by weight of the composition.

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oil content desirably varies inversely, and the other components concentrations vary directly, as does the water content of the composition. Compositions containing percentages of water in the upper portion of the permissible range arenormally advantageous, inasmuch as they possess a greater capacity for taking up water-soluble or water-dispersible contaminants. However, in instances where the compositions are used or stored under extreme temperature conditions, mixtures containing lower proportions of water may be desirable, as such mixtures tend to exhibit greater stability. The water employed in the composition may be ordinary tap water, if desired, although distilled water is preferred, since its capacity for dissolution of water-soluble contaminants is somewhat greater. As implied by the foregoing, it is an important function of the water in the composition to dissolve water-soluble corrosion-inducing contaminants such as inorganic salts. However, the water may function partly or entirely as a carrier for dispersed contaminants.

The base oil or mineral hydrocarbon oil vehicle employed in the composition may be one having substantial volatility at room temperature, such as, for example, petroleum naphtha, mineral spirits (a petroleum solvent having a boiling range from about 150 to about 200 C.), hexane, heptane or kerosene, or it may be one having substantially no volatility at such temperatures, such as, for example, lubricating oil distillates having viscosities ranging from 50 to 3500 SUS at 100 F., or the base oil may comprise mixtures including both types of oils in varying proportions. The nonvolatile oils are employed in the composition when, and to the extent that, it is desired to provide a lasting, protective oil film on the surface of the metal article treated with the composition. Where lubricating distillates of relatively high viscosities are employed, it is normally desirable to reduce the over-all viscosity of the composition by blending into the latter the necessary proportion of a light hydrocarbon diluent of the kind indicated. The mineral oil base or vehicle forms the largest single portion of the composition and is present in amounts ranging from about 49 per cent to The mineral oil vehicle functions as a solvent for the predominantly lipophilic materials inthe composition, as a solvent'or continuous phase in which the aqueous phase is dissolved or dispersed, and as a solvent or dispersant for any oil-soluble or oil-dispersible contaminants deposited on metal surfaces that are treated with the composition.

An alkali metal salt of an oil-soluble sulfonic acid is employed in the composition in amounts of from about 1 to about 10 per cent by weight of the composition. The

' class of alkali metal salts of oil-soluble sulfonic acids is able temperatures by the use of previously formed solutions of the individual additive agents, otherthan water, in a portion of the mineral oil vehicle or baseoil.

The principal components of the composition, from the standpoint of the external functioning thereof, are the mineral oil vehicle and the water. The latter is employed lubricating oil distillates.

well-known and includes salts of oil-soluble aliphatic hydrooarbon sulfonic acids containing at least 8 carbon atoms per molecule, such as, for example, the higher molecular weight naphthene sulfonic acids, and alkyl substituted aromatic sulfonic acids in which the alkyl substituent contains at least 8 carbon atoms, such as the higher molecular weight alkyl benzene sulfonic acids, eg., the wax alkyl benzene sulfonic acids. Commercial mixtures of alkali metal salts of hydrocarbon sulfonic acids, such as sodium petroleum sulfonates, are especially suitable for the purpose of this invention. Such salts have average molecular weightsranging from about 450 to about 650 and are prepared by neutralization of oil-soluble petroleum sulfonic acids resulting from sulfuric acid treatment of These salts and their preparation are known in the art and need not-be discussed in detail, The alkali metal hydrocarbon sulfonate is a strongly hydrophilic material which tends to promote emulsification of thewater in the mineral oil base and which in addition functions to improve the spreading. coefficient and penetrability of the composition. The improvement in the latter property is important, since event highly polished metal surfaces contain microscopicpits and de pressions. which are, capable of-1 retaining. minute quantities of corrosion-inducing contaminants. The sulfonates also impart rust inhibiting properties. to the composition.

An alkanol amine is employed in the; composition in an amount ranging from about 0.25 to about 2.5 per cent by weight of the composition. Alkanol amines included by the invention areprimary, secondary and tertiary alkanol amines whose alkanol substituents contain from 2 to 3 carbon atoms. Monoethanol. amine, diethanol amine, triethanol amine and triisopropanol amine are examples of such compounds. It is considered probable that this component of the composition reacts with the excess of fatty acid in the composition to form an alkanol amine soap having both hydrophilic and lipophilic properties. The alkanol amine soap acts with the alkali metal sulfonate as-a co-emulsifier and assists in maintaining the stability of the composition over a widerange of temperatures. This material also contributes to the wetting properties of the composition.

A fatty acid containing from 12 to 24 carbon atoms is employed in the composition in concentrations of from about 0.75 to about 7.5 per cent by weightof the composition and in excess of a 1:1 mol ratio with respect to the aforesaid alkanol amine. Examples of fatty acids included by the invention are n-dodecanoic acid, stearic acid, oleic acid, linoleic acid, and tetracosanoic. acid. Fatty acids which are liquid at room temperature, such as oleic acid, are preferred in order to facilitate blending at room temperature. However, as heretofore indicated, blending at room temperature of normally solid fatty acids may be expedited by previously dissolving the same in a portion of the mineral oil base. The free fatty acid functions in the composition asa lipophilic co-ernulsifier, and it also increases the viscosity of the oilphase. In addition, the fattywacid improves the stability of the composition to a marked degree.

The composition further includes as an essential; ingredient from about 0.1 to about 1.0 per centby weight of the composition of a. salt of a primary aliphatic amine containing from 8 to. 18 carbon atoms and a dialkyl orthophosphoric acid, the alkyl substituents of which contain from 3 to 10 carbon atoms. Representativeexamples of amine salts included by the invention are n-octyl, ndodecyl, n-octadecyl and n-octadecenyl. amine. salts of din-propyl, di-n-amyl, di-n-capryl and isoamyl isooctyl orthophosphoric acids. The amine salts of commercial amine mixtures, such as cocoamine, a mixture containing predominantly lauryl amine together with lesser amounts of homologous alkyl amines containing from 8 to 18 carbon atoms, are suitable for the purposes of this invention. The amine salt, or alkylammonium dialkyl o-phosphate, employed in the composition functions as a lipophilic rust and corrosion inhibitor. The inhibitors of the particular closs disclosed also function in the composition as stabilizing agents and are essential from this standpoint also, since their omission leads to instability in the final composition.

The herein disclosed corrosion-inhibiting compositions further contain from about 5 to about per cent by weight of the composition of a coupling agent, or mutual solvent for oil and water, selected from the group consisting of 2-butoxyethanol and mixtures thereof with butanol, the 2-butoxyethanol being present in the amount from about 1 to 15 per cent by weight of the composition, and the butanol being present in the. amount of from 0 to 14 per cent by weight of the composition. Although these materials are predominantly hydrophilic, the presence of an influential butyl group in the molecule tends .to provide lipophilic properties thereto to an appreciable extent. The nature of the herein disclosed cou- Gil pling, agents is of great importance from the standpoint of the ultimate function of the composition. The coupling agents disclosed above must be employed in order to provide fully effective results with respect to metal cleansing properties, stability, and/0r protection against corrosion. Mixtures of Z-butoxyethanol and butanol are desirable. from an economy standpoint, but Z-butoxyethanol alone is preferred from the standpoint of its superior performance.

Corrosion-inhibiting compositions included. by this invention are apparently homogeneous, bright or transparent solutions having. a high. degree of stability over a wide range of temperatures. The term solution is used in its normal broad sense to indicate either a true solution, or a colloidal solution-or emulsion. The right ap earance of the composition is indicative of an extremely fine particle size (normally less than about 0.05 p.) for the dispersed phase. The homogeneity andunusual stability of the composition are attributed to the coaction of the various additive components, in the proportions set forth above, to provide the hydrophilic-lipophilic balance required for a bright, stable dispersion. While the exact nature of, and the reasons for, the mutual interaction of the various agents are. not fully understood, owing to the present undeveloped state ofthe technology involved, the outstanding stability of: the herein disclosed complex compositions demonstrates the aforesaid interaction.

The compositionsprepared according to the foregoing description have been. found useful in counteracting .and/or removing; corrosion-inducing, inorganic and or- .ganic materials which-have become deposited upon metal surfaces that are susceptible to corrosion. Specific uses of the herein disclosedcompositions include the removal of corrosive. fingerprint and/ or perspiration residues from, for example, ballbearings and other metal articles. The compositions may also be used. to remove and/or neutralize the effect of residuesaccumulating on the surfaces of,.for example, internal. combustion engine crank shafts, or other forged articles which have been quenched in molten salt baths. The,- compositions of this invention also find use in cleansinggand/or inhibiting corrosion of the surfaces of sinteredmetal objects, thus preventing discoloration. and/ or loosening of subsequently applied metal platingmaterials, due to.the presence of contaminants on the surfaces of the sintered metal objects.

According to oneusage of the invention, the composition is utilized in. the. form of a bath through which the articles to be cleansed and/or protected are passed. The large capacity of the. herein disclosed compositions for contaminants and the unusual stability of the latter over awide range of temperatures, and for protracted periods, afford an exceptionally long and useful life for the composition. in such usage.

The preparation and utility of typical compositions included by this, invention are demonstrated in the following specific examples.

EXAMPLE I Two compositions, composition A andcomposition B, were prepared according to the following make-up:

The foregoing compositions were prepared by admixing the components at room temperature Wlth stirring, the

oleic acid being added last in each instance, until the composition became bright, i. e., free from haze. The light lubricating distillate employed in the foregoing compositions and in composition hereinafter referred to was a low-viscosity, lubricating distillate derived from a Coastal type crude oil. A typical sample of this oil had an API gravity of 23.5", a viscosity of 107.0 SUS at 100'F., 38.3 SUS at 210 F., a flash point (open cup) of 315 F., a fire point (open cup) of 355 F., and a Conradson carbon residue of 0.06 per cent. The cocoamine salt referred to was employed in a lubricating oil solution containing 84 per cent by weight of said salt.

Each of compositions A and B demonstrated the ability to remove fingerprints when subjected to the procedure specified in Military Specifications MIL-C-l5074A. Briefly, this test involves imprinting a synthetic fingerprint upon a low-carbon steel test panel which has been previously cleaned thoroughly. The fingerprint is applied by pressing the roughened face of a rubber stopper which has been moistened with synthetic fingerprint solution upon the surface of the test panel. The synthetic fingerprint solution is made up by dissolving 7 grams of sodium chloride, 1 gram of urea and 4 grams of lactic acid (85 per cent) in equal parts of sufiicient methanol and distilled water to furnish one liter of solution. The fingerprinted test panel is oven-dried. The dried panel is then slushed 2 minutes in the corrosion-inhibiting composition being tested following which the panel is removed and cleansed of the inhibiting composition by slushing in a specified solvent. The test panel is then dried and placed in a 100 per cent static humidity chamber for 24 hours at 77 F. At the end of the 24 hours exposure in the humidity chamber, the panel is examined for rust. No rust or corrosion should appear on the surface of a test panel treated with an etfective inhibitor composition. A control panel, not treated with an efiective inhibitor composition, but otherwise exposed to the same test conditions, exhibits 100 per cent corrosion in the imprinted area. Y

Each of compositions A and B was found to effect complete removal of fingerprints under the conditions of the foregoing test. The results of these tests are shown in the following table:

Table 1 Composition A I B passes.

Fingerprint Removal (MIL-C-15074A) passes...

EXAMPLE II A third test composition, composition C, having the following make-up, was prepared according to the procedure indicated in Example I.

Compositions A, B and C were each tested for heat stability according to the test set forth in Military Specifications MIL-C-l5074A. Briefly, according to this test the compositions are maintained in loosely stoppered pour point tubes at a temperature of 130 F. for 3 days. At the completion of the test the tubes are stoppered and inverted and returned to the original position 6 times and permitted to stand at room temperature for 1 hour.

No stratification should be evident at the end of the .test. The results of the test as applied to compositions A, B and C are indicated below:

The data presented in the foregoing table illustrate the heat stability of the herein disclosed compositions and the criticality of the mutual solvent with respect to this property.

EXAMPLE HI Each of compositions A, B and C were also subjected to the corrosion test specified in Military Specifications MIL-C-l5074A. According to this test standard specimens of aluminum, brass, lead, steel and zinc, having previously been cleaned with naphtha and then with methanol, are weighed and placed in a glass rack which in turn is placed in a glass vessel. The metal test specimens are then covered with the composition being tested, and the glass vessel is placed in an oven maintained at 130 F. for 7 days. At the end of this time the metal specimens are removed from the solution, cleaned with naphtha and then methanol, dried and reweighed. The aforesaid specifications establish the maximum permissible corrosion for each kind of metal. The results of this test are set forth in the following table:

Table 3 Composition A B C Permissible Wt. Loss, Wt. Loss, Wt. Loss, Wt. Loss, nag/em), mgJcrn. mg./cm. mg./om. MIL-C- 15074A Specimen:

Aluminum nil nil nil 0. 2 Brass 0. 1. 21 3.05 2. 0 Lead 7. 45 10. 30 25.26 22. 3 Steel (1020). nil nil nil 0. 2 Zinc 0. 50 2. 65 7.11 8. 5

The data presented in the foregoing table indicate the criticality of the identity of the coupling agent withrespect to the corrosiveness of the composition. Specifically, compositions A and B, prepared in accordance with this invention, are well within the permissible corrosion limits. Composition C on the other hand, differing essentially from compositions A and B only in the nature of the coupling agent, proved unduly corrosive to brass and lead, and was very close to the maximum permissible limit with zinc.

In addition to the properties demonstrated in the foregoing specific examples, compositions prepared accord ing to the invention also possess low temperature stability, are easily removable from metal surfaces and possess no offensive or disagreeable odors. Moreover, compositions prepared according to this invention are capable of neutralizing the corrosive effect of corrosioninducing contaminants, even when said contaminants are not actually displaced from the surface of the metal.

Other suitable corrosion-inhibiting compositions can be prepared similarly as in the foregoing examples by substitution of other components from the herein disclosed classes of materials, in the same proportions, or in other proportions disclosed herein as having utility. Other agents that do not interfere with the functions of the above-disclosed components may be added to the composition in order to further improve the composition with respect to one or more properties thereof.

Numerous modifications of the herein disclosed com positions can be resorted to without departing from the spirit of the invention. -Accordingly, the invention is 1. A bright, stable corrosion-inhibiting composition comprising about 49 to about 88 percent by weight of the composition of a mineral oil base, and having. incorporated therein from about 5 to about 15 percent by Weight of water, from about 0.25 to about 2.5 per cent by weightof an alkanol amine selected from thegro'up consisting of primary, secondary and tertiary alkanol amines whose alkanol substituents .contain. from 2 to 3 carbon atoms, from about 0.1.to..about. 1.0 per cent by weight of a salt of a primary aliphatic aminelcontaining from 8 to 18 carbon atoms and a dialkyl' ester of orthophosphoric acid,the alkyl substituents of which con tain from 3 to 10 carbon atoms, from about 1 to about 10 per cent byweightof an alkali metal salt of an oilsolublesulfonicacid, from about 0.75 to-about 7.5 per 7 cent by-Weight of afattyacidcontaining from 12 'to 24 carbon atoms, the fatty acid-:a-lkanol amine mol ratio being inexcess of 1:1,:at0tal of-about 5 to about 15 per cent by. Weight of a coupling agent selected fromthe group consisting of 2-butoxyethanol and mixturesthereof with butanol,-the Z-butoxyethanolbeing present in an amount of from about 1 to about 15- per cent by' weight, and the butanol being present in an-ramount' of from about to about 14per cent by weight.

thelcornposition of a mineral oil base, and having incorporat'ed therein from about to about. .15 .per .cent' by.

weight of Water; from about 0.25 to about2.5 per cent by weight of triethanol amine, from about 01 to about 1.0 per cent by'weiglit of the cocoamine salt of .2-etliylhexyLli-methYlbutyl orthophosphorie acid, from about 1 to about percent by weight of sodium petroleum sul- Light lubricating dist'illateoil 35.00 Mineral spirits -1 34.42 Oleic acid 5.50 Triethanol amine 1.75 i Cocoamine salt of 2-ethylhexyl,3-methy1butyl 'ophosphoric acid-(84% mineraloil solution) Sodium salt of oil-soluble petroleum sulfonic acids 3.5 2-butoxyethanol 7.5 Water 12.0

2. A bright, stable corrosion-inhibiting composition comprising about 49 to about 88 per cent by weight of the composition of a1 mineraloil base, and having incorporated therein from about 5 to'about 15 per cent by weight of water, from about 0.25 to about 2.5 per cent by weight of triethanol amine, from about 0.1 to about 1.0 per cent by weight of the cocoarnine salt ofZ-ethyly hexyl,3-methylbuty1 orthophosphoric acid, from about 1 to about 10-per centbyweight of' sodium petroleum sulfonate, from about 0.75 to about 7.5 percent by weight of oleic acid, the oleic acid:triethanol amine mol ratio being in excess of 1:1, a total of about 5 to about 15 per cent by weight of a coupling agent selectedfrom the group consisting of Z-butoxyethanol and mixtures thereof with butanol, the Z-butoxyethanol being present in an amount of from about 1 to about 15 per cent by weight, and the butanol being present in an amount of 'from about 0 to about 14per cent by weight.

3. .A bright, stable corrosioneinhibiting composition comprising about 49 to about 88 per cent by weight of fonate, 'from about 0.75 to about 7.5 per cent by weight of oleic acid, .the oleic acidztriethanol amine mol ratio being in excess of 1:1, and from about 5 to about 15 per cent by weight of Z-butoxyethanol. p p

. 4. .A bright, stable corrosion-inhibiting composition having thefollowing approximate make-up:

Per cent by Weight 5. A bright, stable corrosion-inhibiting. composition Light lubricating distillate oil 35.00 i Mineral spirits 31.92 Oleic acid 5.50 Triethanolamine i 1.75 Cocoamine salt of Z-ethylhexylfl-methylbutyl 0- phosphoricacid ('8 4% mineral oil solution) i 0.33 Sodium salt of "oil-soluble petroleum sulfonic "acids 3.5 Butanol' 5.0 Z-butoxyethanol 5.0 Water 12.0

References Cited in'the file of this patent UNITED STATES PATENTS 2,080,299 Benning May 11, 1937 2,402,793 White June 25, 1946 2,408,971 Duncan Oct. 8, 1946 2,574,956 Bishop Nov. 13, 1951 

1. A BRIGHT STABLE CORROSION-INHIBITING COMPOSITION COMPRISING ABOUT 49 TO ABOUT 88 PER CENT BY WEIGHT OF THE COMPOSITION OF A MINERAL OIL BASE, AND HAVING INCORPORATED THEREIN FROM ABOUT 5 TO ABOUT 15 PER CENT BY WEIGHT OF WATER, FROM ABOUT 0.25 TO ABOUT 2.5 PER CENT BY WEIGHT OF AN ALKANOL AMINE SELECTED FROM THE GROUP CONSISTING OF PRIMARY, SECONDARY AND TERTIARY ALKANOL AMINES WHOSE ALKANOL SUBSTITUENTS CONTAIN FROM 2 TO 3 CARBON ATOMS, FROM ABOUT 0.1 TO ABOUT 1.0 PER CENT BY WEIGHT OF A SALT OF A PIMARY ALIPHATIC AMINE CONTAINING FROM 8 TO 18 CARBON ATOMS AND A DIALKYL ESTER OF ORTHOPHOSPHERIC ACID, THE ALKYL SUBSTITUENTS OF WHICH CONTAIN FROM 3 TO 10 CARBON ATOMS, FROM ABOUT 1 TO ABOUT 10 PER CENT BY WEIGHT OF AN ALKALI METAL SALT OF AN OILSOLUBLE SULFONIC ACID, FROM ABOUT 0.75 TO ABOUT 7.5 PER CENT BY WEIGHT OF A FATTY ACID CONTAINING FROM 12 TO 24 CARBON ATOMS, THE FATTY ACID: ALKANOL AMINE MOL RATIO BEING IN EXCESS OF 1:1 A TOTAL OF ABOUT 5 TO ABOUT 15 PER CENT BY WEIGHT OF A COUPLING AGENT SELECTED FROM THE GROUP CONSISTING OF 2-BUTOXYETHANOL AND MIXTURES THEREOF WITH BUTANOL, THE 2-BUTOXYETHANOL BEING PRESENT IN AN AMOUNT OF FROM ABOUT 1 TO ABOUT 15 PER CENT BY WEIGHT AND THE BUTANOL BEING PRESENT IN AN AMOUNT OF FROM ABOUT 0 TO ABOUT 14 PER CENT BY WEIGHT. 